Computer-generated images find use in many different industries to model surfaces and solids. In the medical field, computer imaging is used in combination with ultrasound imaging, magnetic resonance imaging or other medical imaging technology to display, analyze and organize the data these medical imaging technologies provide. For example, ultrasound machines use ultrasonic wave, i.e. sonar, to scan a patient's body. The data thus obtained is then analyzed by physicians to assist the physicians in their diagnosis and treatment of patients. Ultrasound can be used to view a fetus, blood-flow patterns in arteries, or to scan organs for irregularities such as cysts, etc.
Typically, a three dimensional image is displayed to a user by being projected on a two dimensional surface such as a screen or a print out. Computer systems have been devised that permit the user to take different cross-sectional views of the image, thereby enabling a user to view a portion of the three dimensional image by choosing one or more cross-sectional views. Some computer systems permit the user to geometrically transform the image by rotating, translating and scaling the image, and also permit the user to take cross-sectional views at different orientations, such that the user can sequentially view the three-dimensional image using a series of oblique planes. Other computer systems take a different approach; instead of showing a cross-section of the three dimensional image, they “render” the volume by making part of the volume transparent or translucent such that points under those parts are revealed. In a maximum intensity display, for example, the highest intensity points along a line parallel to the line of sight of the user are shown, similar to an x-ray picture of a foot.
While three dimensional images provide a wealth of information, filtering out the information that is of interest from irrelevant information can be very time-consuming. This is especially the case for medical images in which the feature of interest is often obscured from clear view by other physical features. A typical method of eliminating irrelevant portions of three-dimensional images is through user selection of portions of the image to scalpel away from a displayed view of the image. Based upon one or more displayed views of the image, the user selects a series of points defining an enclosure. In a two-dimensional image, the selected points define a shape, whereas in a three-dimensional image, the selected points define a volume. The image processing system then eliminates any image data within the selected enclosure and re-displays the view(s) of the image. The user may then select points to define another enclosure to eliminate. In such a manner, the user pares away unwanted portions of the image. Among the disadvantages of this method are the time required of the user to select the enclosures and the difficulty of accurately selecting the unwanted areas without also scalpelling away portions of the feature of interest.
Accordingly, there remains a need for a system and method of quickly and easily analyzing and manipulating computer-generated images in order to filter out as much irrelevant information as possible from the images and display only the region of interest.